The Chest Trapper is a chest-mounted cannon that fires out an ectoplasmic clamp.
During the Squid Ghost case, Professor Dweeb made a second attempt to capture Slimer using the Chest Trapper. Dweeb did manage to capture Slimer but he escaped by drinking an entire jug of water. Once free, Slimer then doused Dweeb in water. The Chest Trapper was overloaded and sucked up Elizabeth.